Is MSG really harmful to the brain?

MSG! I love the taste of MSG :D. I grew up in an Asian household, so the seasoning has been a staple in my food for my entire life. It brings this unique savory flavor out of meats and goes well in pretty much any dish that has meat. (Tip: You only want to add a small pinch of it to your dish. Any more than that and it will just taste really weird.)

I’ll start with all the good stuff before I dive into what caused the MSG scare a number of years ago. Monosodium glutamate (MSG for short) is a type of salt that is also known by the name umami, and it’s found in ripe tomatoes, cheeses, cooked and aged meats, seaweed, and other food sources.1 Apparently, the reason it tastes so delicious is because it is the fifth basic taste in addition to the usual sweet, sour, salty, and bitter.2,3 That means that you have taste buds made for experiencing this salt in all its glory.

 I agree that tomatoes are awful. We should absolutely remove this source of MSG from our diets :P!
I agree that tomatoes are awful. We should absolutely remove this source of MSG from our diets!

So why are restaurants all taking MSG out of their meals?

Well, if we’re being highly technical…they’re not, since it’s naturally present in all sorts of foods. They are, however, taking out the addition of this extra salt to the meal:

This is what it looks like when you buy it in a package from the grocery store--nicely purified and ready to add to your cooking.
This is what it looks like when you buy it in a package from the grocery store–nicely purified and ready to add to your cooking.

What initially caused us to fear these tiny white crystals?

It looks like it was originally due to an article from 1969 that showed glutamate would destroy neurons in the brain when administered subcutaneously to infant mice.4 It seems like the excess of glutamate overstimulated the neurons, and that caused them to figuratively explode. However, it’s important to note that the scientist directly injected glutamate in infant mice, so this is very different from an adult eating glutamate as part of their meal.

Since these initial findings, a LOT of scientific research has been conducted investigating the effects of MSG on the brain. But for practical purposes, in order for MSG to have an effect on the brain, it must first reach the brain after being ingested through the mouth. This is what we refer to as crossing the blood brain barrier (BBB) in science, which is a really huge hurdle for central nervous system medicine development.5 But how well does glutamate cross this barrier? It seems not very well at all, as there are very strict and effective channel systems in place.6 In fact, it appears that MSG is more effectively removed from the brain than it is introduced to it.7

What does this mean in simpler terms? Think about the last time you went to a crowded event. You had to go through a gate that was manned by staff who took your tickets, verified them, and let you in. Maybe they even stopped letting people in when the venue reached maximum capacity. On the other hand, you could leave at any time through any of the exits. Basically, your brain already has these systems in place to make sure that the situation inside is safe!

Table salt (Sodium chloride) is composed of two ions: Na+ and Cl-. Monosodium glutamate also shares that sodium ion, but has a glutamate molecule instead of the chloride ion. Glutamate (or glutamic acid) is an amino acid, and thus it is a building block of life!
Table salt (Sodium chloride) is composed of two ions: Na+ and Cl. Monosodium glutamate also shares that Na+ ion, but has a glutamate molecule instead of the Cl ion. Glutamate (or glutamic acid) is an amino acid, and thus it is a building block of life!

What’s the final verdict?

So while it is true that excess glutamate would do some damage to your brain, it would first have to get there in excessive quantities. I can’t even wrap my head around how much MSG you would have to ingest in order for it to have a chance to overwhelm your brain like that, but I’m certain it’d be more than what’s pictured above. And I don’t know about you…but I don’t really eat MSG in handfuls at a time.

So, that should be the end of the argument, right? If it’s not reaching your brain, then it isn’t doing anything to it, right? More or less, yes. With the way we cook using MSG (adding a tiny pinch to a whole dish), I am not concerned at all about whether or not it will damage my brain. But as is the rule for almost everything in science–always in moderation. If you overload the circuits, of course the system is going to bug out and explode. Your body is no exception to that rule.

– The Scientist Next Door

References:

  1. Brosnan, J. T., Drewnowski, A. & Friedman, M. I. Is there a relationship between dietary MSG obesity in animals or humans? Amino Acids 46, 2075–2087 (2014).
  1. Yamaguchi, S. & Ninomiya, K. Umami and food palatability. J. Nutr. 130, 921S–6S (2000).
  1. Kurihara, K. Glutamate: from discovery as a food flavor to role as a basic taste (umami). Am. J. Clin. Nutr. 90, 719S–722S (2009).
  1. Olney, J. W. Brain lesions, obesity, and other disturbances in mice treated with monosodium glutamate. Science 164, 719–21 (1969).
  1. Pardridge, W. M. The blood-brain barrier: Bottleneck in brain drug development. NeuroRX 2, 3–14 (2005).
  1. Smith, Q. R. Transport of glutamate and other amino acids at the blood-brain barrier. J. Nutr. 130, 1016S–22S (2000).
  1. Hawkins, R. A. The blood-brain barrier and glutamate. Am. J. Clin. Nutr. 90, 867S–874S (2009).
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